In recent years, lower power consumption of electronic devices has been required. In a switching power supply circuit used as a power supply of an electronic device, power consumption can be lowered by controlling the switching operation of a switching element. As a conventional switching power supply circuit, a suggested technique reduces the switching frequency of a switching element in a standby mode, thereby reducing power consumption and an abnormal harsh noise (e.g., a buzz) of a transformer (see, for example, Patent Document 1).